Etching machine and method for making printing plates

ABSTRACT

THIS ETCHING MACHINE INCLUDES AN ETCHANT TANK HOUSING AN ETCHANT SPRAY SYSTEM AND A WORKPIECE SUPPORT SYSTEM. THE SPRAY SYSTEM INCLUDES AT LEAST ONE UPRIGHT ROTATABLE TUBULAR BODY FORMED FROM COAXIAL CYLINDERS CLOSED AT THE UPPER END TO PROVIDE A SPRAY CHAMBER. THE LOWER END OF THE TUBULAR BODY IS IMMERSED IN THE ETCHENT BATH AND HELICAL VANES WITH IN SPRAY CHAMBER DELIVER ETCHANT UNDER PRESSURE THROUGH THE SPRAY APERTURES AS THE TUBULAR BODY ROTATES. THE ROTATION OF THE TUBULAR BODY IS ACCOMPLISHED BY AN AXIAL DRIVE SHAFT ENCLOSED AT ITS LOWER END BY A WELL TUBE WHICH EXTENDS ABOVE THE ETCHENT LEVEL TO PRECLUDE ETCHANT LEAKAGE. THE WORKPIECE SYSTEM INCLUDES A ROTATABLE ELEMENT HOLDING THE WORKPIECE IN THE VERTICAL PLANE AND MOVABLE ALONG A TRACK TO REVOLVE THE WORKPIECE AS IT PASSES THROUGH THE SPRAY PATH.

Sept. 5, 1972 c. R. HlLLHoUsE 3,689,333

ETCHING MACHINE AND METHOD FOR MAKING PRINTING PLATES Filed Aug. 24, 1970 S'Sheets-Sheet 1 ATTORNEYS FIG. 2

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Sept. 5, 1972 C. R. HILLHOUSE E'ICHING MACHINE AND MTHOD FOR MAKING PRINTING PLATES Filed Aug. 24, 1970 I5 Sheets-Sheet 2 NVENTOR CHARLES R. HILLHOUSEV BY v ATToRNEvs Sept. 5, 1972 C. R. HILLHOUSE ETCHING MACHINE AND METHOD FOR MAKING PRINTING PLATES Filed Aug. 24, 1 970 5 Sheets-Sheet United States Patent O U.S. Cl. 156-14 16 Claims ABSTRACT OF THE DISCLOSURE This etching machine includes an etchant tank housing an etchant spray system and a workpiece support system. The spray system includes at least one upright rotatable tubular body formed from coaxial cylinders closed at the upper end to provide a spray chamber. The lower end of the tubular body is immersed in the etchant bath and helical vanes within the spray chamber deliver etchant under pressure through the spray apertures as the tubular body rotates. The rotation of the tubular body is accomplished -by an axial drive shaft enclosed at its lower end by a well tube which extends above the etchant level to preclude etchant leakage. The workpiece system includes a rotatable element holding the workpiece in the -vertical plane and movable along a track to revolve the workpiece as it passes through the spray path.

BACKGROUND OF THlEl INVENTION This invention relates in general to an etching machine and in particular to an etchant distribution system for delivering etchant to a workpiece.

The process of etching is commonly carried out by applying an acid etchant to a plate or workpiece. Most photo-engravers using etching machines which employ a paddle system to distribute the etchant by throwing etchant bath into contact with the workpiece. This method is slow because paddles deploying the liquid are only effective to a given angular speed. Beyond this point cavitation prevents the conventional paddle etcher from increasing the volume of liquid to be distributed onto the workpiece. Etch rates in a paddle type machine, based on thousandths of an inch per minute, increases with higher paddle revolutions per minute until an optimum speed is achieved beyond which the etch rate diminishes due to paddle cavitation. Further, in machines of this type, the results are partially governed by the paddle dip, and hence the depth of the bath becomes critical since it regulates the amount of etchant distributed to the workpiece.

SUMMARY OF THEl INVENTION This etching machine considerably reduces the etching period in comparison with the fastest etching processes currently in use, particularly those using a paddle distribution system.

Further, the bath depth is no longer critical as it is in the case with the conventional paddle system and the application of the etchant by rotary spray, rather than by splashing, leads to a more eflicient distribution of the etchant.

The provision of a vertical rotary cylinder is a great advantage, particularly because the lower portion of the cylinder, which constitutes a rotary pump, is immersed deep in the etchant liquid and is not subject to cavitation at higher speeds. Thus, the force of the spray distribution may thereby be increased, resulting in faster etch rates.

Another advantage of the rotary cylinder is that it provides a uniform pattern of the spray distri-buted in a 360 circle around its perimeter. This enables the workpieces to be supported vertically on both sides of the cylinder, thereby increasing the efficiency of the system.

Patented Sept. 5, 1972 The provision of a shaft enclosure means precludes leakage from the shaft journals and permits the spray units to rotate about a vertical axis, even though the shafts are operating below the etchant level. The leakage problem inherent in virtually all prior systems is thus eliminated.

This etching machine is simple in construction and operation and is economical to maintain because longer bath life is obtained and maintenance costs are low.

'Ihe etching machine includes a tank for an etchant bath. Support means is provided within the tank to hold a workpiece in movable adjacent relation to a rotatable spray means. The rotatable spray means includes a spray chamber formed from coaxial inner and outer cylindrical walls and pum-p means delivers etchant into the spray chamber for delivery through the spray apertures onto the workpiece. Shaft means is attached to the rotatable tubular body to rotate said body.

The support means includes a track and means rotatable relative to the track. Said rotatable means is attached to the workpiece and is translationally movable relative to the track to displace the workpiece transversely of the axis of rotation of the tubular body. The workpiece is thereby subjected to both rotational and translational movement relative to the rotatable spray means and the workpiece revolves, as it moves through the etchant spray.

The spray means houses a helical vane coaxially disposed relative to the tubular body and extending upwardly to provide pump means delivering etchant into the spray chamber.

The tank includes upper and lower walls and a drive shaft axially disposed of the tubular body extends between said walls. The lower wall includes an aperture receiving the drive shaft and a well tube is attached to said lower wall in upwardly extending relation so that the remote end of the well tube is disposed above the etchant level and precludes leakage of the etchant material from the lower wall aperture.

BRIEF DESCRIPTION OF THE DRAWINGSA \FIG. 1 is an elevational View of the etching tank with the front removed to reveal the etching distribution system;

FIG. 2 is a `cross sectional view taken on line 2-2 of FIG. l;

FIG. 3 is a cross sectional view taken on line 3 3 of FIG. 1;

FIG. 4 is an enlarged fragmentary View 0f the workpiece support mechanism;

FIG. 5 is a cross sectional view taken on line 5-5 of FIG. 4;

FIG. 6 is an enlarged cross sectional view taken on the interior of the spray unit, and

FIG. 7 is an enlarged view of the exterior of the spray unit.

DESCRIPTION OF T-HE PREFERRED 'EMBODIMENT Referring now by characters of reference to the drawings and first to FIG. 1, it will be understood that the etchant tank 10 includes upper and lower walls 11 and 12, opposed end walls 15 to provide a closed container for the etchant bath 16 and a housing for the etchant distribution system, which distributes etchant to the workpiece 17, and the workpiece support system.

The etchant distribution system includes a plurality of identical spray units 20, three rows of three each in the preferred embodiment, and a plurality of inner and outer workpiece support assemblies 21 and 22 respectively. The assemblies 21 and 22 which comprise the workpiece support system are substantially similar and therefore,

wherever possible, the same reference numerals will be utilized to indicate corresponding parts.

Each of the spray units 20 is rotatively mounted within the tank by a shaft 23, which extends between the upper and lower tank walls 11 and 12 and constitutes drive means rotating the spray units 20. Each shaft 23 is held in journaled relation to the tank 10 by a retaining collar 24 attached to the upper wall 11 and each shaft 23 depends below the lower wall 12. A drive connection element 25, which is connected to a drive unit such as an electric motor (not shown), provides a means of rotating each shaft 23.

An individual spray unit 20 is shown in some detail in FIGS. 6 and 7. Each of said units 20 includes an inner cylindrical wall 26 coaxially disposed in spaced relation from an outer cylindrical wall 27 to provide a compound tubular element 28 defining an annular spray chamber 30. The outer Wall 27 includes a plurality of spray apertures 31 distributed evenly over the surface of said outer wall 27. A spacer element 32, which is attached to the shaft 23 by means of a plurality of set screws 33, provides a means of attaching the compound tubular element 28 to said shaft 23. As shown clearly in FIG. 6, this attachment is achieved by means of fasteners 34 extending between the outer wall 27 and the spacer 32, and fasteners 35 extending between the inner wall 26 and said spacer 32. The spacer 32 fulfills a further function in that it includes an annular portion 35 extending between the inner and outer walls 26 and 27 and constituting closure wall means. A second spacer 36, attached to the shaft 23 and also to the inner wall 26 as by screws 37, provides further attachment between the shaft 23 and the compound tubular element 28.

-At its lower end, the inner wall 26 includes a frustoconical portion 40 leading into a reduced diameter lower end portion 41. The outer wall 27 has substantially parallel sides and consequently, the reduction of the diameter of the inner wall 26 at the lower end, provides an increased diameter spray chamber portion 42.

The lower portion 42 of the spray chamber 30 extends from a point substantially coincident with the etchant level 16 to the lower end 43 of the compound tubular element 28. The relatively narrow portion of the spray chamber 3G above the lower portion 42l is provided with a single helical vane 44 and the lower portion 42 is provided with a pair of helical vanes 45 and 46. Said helical vanes 44, 45 and 46 constitute pump means delivering etchant into the spray chamber 30 under pressure for diffusion from the spray apertures 31 on rotation of the spray unit 20. The helical vanes 44, 45 and 46 are attached to the inner wall 26 as by Welding.

The lower tank wall 12 includes an aperture 47 receiving the shaft 23. In order to prevent any leakage of the etchant 16 from the tank 10, a cylindrical well tube 50 is peripherally disposed about said aperture 47 and sealingly attached, as by welding, to said lower wall 12. The well tube 50 extends substantially above the etchant level and is slidingly received within the reduced diameter portion 41 of the inner wall. Thus, the spray unit 20 rotates about said well tube 50.

Each of the spray units 20 is provided with a frustoconical skirt 51 slightly below the etchant level. This skirt S1 provides an anti-cavitational device precluding the ingress of air into the interior of the spray chamber 30.

Referring now to FIGS. 1 and 2, it will be understood that the support assemblies 21 and 22, which hold the workpieces 17 adjacent the rotating spray units 20, include an inverted U-shaped frame element 52 having a bight portion providing a horizontal base 53 for a `wheel and track assembly, shown in detail in FIGS. 4 and 5.

In the preferred embodiment, the wheel and track assembly is provided by a pair of pinions 54 riding on a pair of opposed rack elements 55. The rack elements 55 are mounted on inwardly turning angle elements 56 which are attached to the base 53 as by welding. The pinions 54 are interconnected by a shaft 57, each pinion including a boss 60 provided with a set screw 61 for this purpose. It will be understood that the pinions 54 and the shaft 57 rotate together as the pinions 54 ride the rack 55. A turntable 62, which is attached to the shaft 57 by a set screw 63, also rotates with the pinions 54 and provides a means of revolving the workpiece 17 attached to the turntable 62 as by clips (not shown). In the preferred embodiment, motion is imparted to the pinions 54 by means of a push-pull rod 64 which operates as a connecting rod and may be actuated by conventional reciprocation mechanism (not shown). The push-pull rod 64 is connected to the pinions 54 by means of a U-shaped link 65, which includes apertured arms 66 receiving the pinion bosses 66 in journaled relation. The push-pull rod which includes a T-shaped tubular head 67, is connected between the arms 66 by means of a pin 70 passing through said tubular head 67. A stop plate 71 is attached to the bight of the U-shaped link 65 in outwardly extending relation thereto, said extending portion providing opposed lips 69 overlapping the inwardly facing angles 56 and providing a means of retaining the pinions 54 in engagement with the rack elements 55. `It will be understood that a push-pull force applied to the push-pull rod 64 results in the travel of the pinion 54 along the rack 55 imparting translational and rotational motion to the workpiece 17. In the preferred embodiment, the stroke of the push-pull rod 64 is substantially equal to the tooth diameter of the pinion 54 so that one cycle of motion of the push-pull rod 64 rotates the workpiece 17 one revolution counterclockwise as the push-pull rod travels in a forward direction, and one revolution clockwise as the push-pull rod moves in the reverse direction (FIG. 2). As a practical matter, in the preferred embodiment, the distance X-Y indicated in FIG. 5 is substantially onehalf of the distance between the outermost spray units 20 of a transverse row. This range of movement insures maximum spray distribution onto the workpiece 17 as indicated in FIG. 2.

It is thought that the functional advantages and structural features of this etching machine have become fully apparent from the foregoing `description of parts, but for completeness of disclosure, the operation will be briey summarized.

T he provision of nine rotating spray units 2t), as shown in the preferred embodiment, provides suiiicient diffusion capability to accommodate the etching requirements for six workpieces 17 but obviously, the etching machine is not limited to this arrangement. The spray units 20 rotate about xed vertical axes and etchant is delivered into each unit 2t) in the ow path indicated in FIG. l by lift pump action provided by the interior vanes 44, 45 and 46 which scoop up the etchant and diffuse it under pressure from the spray aperture 31 substantially as indicated in FIG. 3. The closed nature of the spray chamber 30, results in the outward spraying of the etchant under considerable pressure, it being understood that the pressure is related to the angular speed at which the spray units 20 rotate.

During the rotation of the spray units 20, the Workpieces 17 disposed adjacent said units 20 are drawn back and forth by means of push-pull rod 64 and, because of the rack and pinion assembly, the workpieces 17 are also revolved. Thus, the workpieces 17 experience considerable motion relative to the dilfused, pressurized etchant with the consequence that the distribution is at maximum efficiency. In addition, the lvertical orientation of the workpieces 17 greatly facilitates the drainage of etchant from said workpieces 17 into the etchant bath. Further, because of the force with which the etchant is impinged against the workpieces 17, the etching speed .is greatly increased so that the production rate of photo-engraved plates is more than doubled compared with conventional paddle-type machines and etching rates in excess of 0.01 inch per minute have been achieved.

With a screw-type of pump, it is obviously an advantage to have an arrangement which permits the rotation of each of the spray units 20 about a vertical axis. This arrangement is made possible by the provision of well tubes 50, which eliminate sealing problems between the rotating shaft 23 and the journal apertures 47 in the lower tank wall 12. Further, because the spray units 20 rotate about associated well tubes 50, said tubes S0 provide a stabilizing means and in addition, serve as a guide in the alignment of associated spray units 20.

Each of the drive shafts 23 can be operated by individual motors. Alternatively, the shafts 23 can be coupled together for operation by a single power source.

I claim as my invention:

1. In an etching machine for etching a workpiece:

(a) a tank for an etchant bath,

(b) support means in the tank adapted to hold the workpiece,

(c) spray means adapted to be disposed adjacent the workpiece and including a rotatable spray chamber having a plurality of spray apertures with axes directed sequentially toward and away from. the workpiece to distribute etchant in a 360 spray pattern as the spray chamber rotates,

'(d) pump means delivering etchant into the spray chamber and through the spray apertures,

(e) drive means rotating the spray means, and

(f) means for revolving the workpiece support means relative to the spray, the support means being aligned in a plane parallel to the rotative axis of the spray means.

2. An etching machine as defined in claim 1, in which:

(t) the spra'y means includes an elongate tubular body providing the spray chamber and having a longitudinal axis of rotation, and

(g) the drive means includes shaft means axially aligned with the longitudinal axis of the tubular body and attached thereto to rotate said body.

3. An etching machine as defined in claim 2, in which:

(h) the elongate tubular body includes substantially l peripherally continuous spaced inner and outer walls deiining the spray chamber.

4. An etching machine as dened in claim 1, in which:

(f) the spray means includes a substantially upright elongate tubular body providing the spray chamber,

(g) the drive means includes a shaft means coaxially disposed of the elongate tubular body and attached thereto to rotate said tubular body,

(h) the tank includes an aperture adapted to be disposed below the etchant level and receiving said shaft means, and

(i) well means adapted to extend above the etchant level is peripherally disposed about said aperture and sealingly attached to the tank to preclude etchant leakage from said aperture.

5. An etching machine as dened in claim 1, in which:

(f) the spray means includes an elongate upwardly extending tubular body having coaxially spaced inner and outer walls, at least partially dening the spray chamber, and

(g) the pump means includes a helical vane coaxially disposed between said inner and outer walls in upwardly extending relation to lift etchant above the etchant bath level on rotation of said tubular body.

6. In an etching machine for etching a workpiece:

(a) a tank for an etchant bath,

(b) support means in the tank adapted to hold the workpiece,

(c) spray means adapted to be disposed adjacent the workpiece and including a rotatable spray chamber having a plurality of spray apertures with axes directed sequentially toward and away from the work- 6 piece to distribute etchant in a 360 spray pattern as the spray chamber rotates,

(d) pump means delivering etchant into the spray chamber and through the spray apertures,

(e) drive means rotating the spray means, and

(f) the support means including means rotating the workpiece and translationally displacing the axis of rotation of said workpiece along a substantially straight path.

7. In an etching machine for etching a workpiece:

(a) tank for an etchant bath,

(b) support means in the tank adapted to hold the workpiece,

(c) spray means adapted to be disposed adjacent the workpiece and including a rotatable spray chamber having a plurality of spray apertures with axes directed sequentially toward and away from the Workpiece to distribute etchant in a 360 spray pattern as the spray chamber rotates,

(d) pump means delivering etchant into the spray chamber and through the spray apertures,

(e) drive means rotating the spray means, and

(f) the support means including a substantially straight track and a wheel movable on said track, said wheel including an axle means adapted to support and rotate the workpiece as the wheel travels the track whereby the workpiece is displaced translationally and rotatively.

8. In an etching machine for etching a workpiece:

(a) a tank for an etchant bath,

(b) support means in the tank adapted to hold a workpiece,

(c) spray means including a rotatable tubular body having an axis of rotation and having a plurality of spray apertures orbiting about said axis of rotation, said body being adapted to be disposed adjacent the workpiece, the axes of said spray apertures being directed sequentially toward and away from said workpiece to distribute etchant in a 360 spray pattern as the body rotates,

(d) delivery means delivering etchant into the tubular `body and through the spray apertures,

(e) drive means rotating the tubular body, and

(f) means for revolving the support means relative to the spray, the support means being aligned in a plane parallel to the axis ot rotation of the tubular body.

9. An etching machine as defined in claim 8, in which:

(f) the axis of rotation of the tubular body is substantially upright and said body includes a spray chamber having an inner cylindrical wall, an outer cylindrical wall and a closure wall extending between said inner and outer Walls, and

(g) the delivery means includes a helical vane coaxally disposed within said spray chamber.

10. In an etching machine for etching a workpiece:

(a) a tank for an etchant bath,

(b) support means in the tank adapted to hold a workprece,

(c) spray means including a rotatable tubular body having an axis of rotation and having a plurality of spray apertures orbiting about said axis of rotation, said body being adapted to be disposed adjacent the workpiece the axes of said spray apertures being directed sequentially toward and away from said workpiece to distribute etchant in a 360 spray pattern as the body rotates,

(d) delivery means delivering etchant into the tubular body and through the spray apertures,

(e) drive means rotating the tubular body, and

(f) the support means being adapted to hold the workpiece substantially upright and including a substantially horizontal track and an axle translationally displaceable relative to the length of said track, said axle being attached to the workpiece to rotate said workpiece during said translational displacement.

11. In an etching machine for etching a workpiece:

(a) a tank for an etchant bath,

(b) a plurality of rotatable tubular bodies disposed in spaced relation, each body including:

(1) inner and outer cylindrical Walls and an end closure wall defining an annular spray chamber,

(c) a helical, upwardly extending vane disposed within each spray chamber to lift the etchant above the etchant bath level on rotation of said tubular bodies,

(d) drive means including a plurality of drive shafts coaxially disposed of and attached to associated tubular bodies to rotate said bodies, and

(e) support means in the tank adapted to hold a workpiece in movable transverse relation to said rotating tubular bodies.

12. A11 etching tank as defined in claim 11, in which:

(f) the support means includes means rotating said workpiece.

13. An etching machine as defined in claim 11, in

which:

(f) the tank includes a lower wall having a plurality of apertures, each of said apertures receiving an associated drive shaft, and

(g) a plurality of well tubes is attached to the lower wall, each of said well tubes being peripherally disposed about an associated aperture and drive shaft, each of said Well tubes extending above the etchant level to preclude leakage from its associated aperture.

14. An etching machine as defined in claim 11, in

which:

(f) the tank includes upper and lower walls having a plurality of aligned apertures,

(g) each of the drive shafts extends between said upper and lower walls in journaled relation to associated pairs of said apertures, and

(h) a plurality of well tubes is attached to the lower wall, each of said tubes being disposed about an associated lower wall aperture and shaft and extending within an associated inner cylindrical Wall upwardly above the etchant level to substantially preclude lateral movement of the associated tubular body and preclude leakage from said associated lower Wall aperture.

15. A method of etching a photoengraved plate comprising the steps of:

(a) directing an etchant spray outwardly from a longitudinal axis substantially parallel to the surface of the plate, and

(b) rotating the etchant spray through 360 about said longitudinal axis to direct it sequentially toward and away from the surface of the plate and distribute etchant in a 360 spray pattern during each revolution.

16. A method of etching as defined in claim 15 including the additional step of:

(c) moving the surface of the plate through the spray in a substantially straight line transverse to said lungitudinal axis.

References Cited UNITED STATES PATENTS 2,995,851 8/1961 Dirats 134-144 3,327,721 6/1967 Carlson 134-111 FOREIGN PATENTS 216,083 10/ 1957 Australia 156-345 JACOB H. STEINBERG, Primary Examiner U.S. Cl. X.R. 134-144; 156-345 

